1. Field of the Invention
Embodiments of the present invention generally relate to a method and apparatus for electrochemical mechanical processing, and more specifically, to a contact assembly and method for applying a bias to a workpiece, such as a substrate and the like, during an electrochemical mechanical process.
2. Description of the Related Art
Electrochemical mechanical planarizing (ECMP) is a technique used to remove conductive materials from a substrate surface by electrochemical dissolution while concurrently polishing the substrate with reduced mechanical abrasion compared to conventional planarization processes. ECMP systems may generally be adapted for deposition of conductive material on the substrate by reversing the polarity of the bias. Electrochemical dissolution is performed by applying a bias between a cathode and a substrate surface to remove conductive material from the substrate surface into a surrounding electrolyte. Typically, the bias is applied to the substrate surface by a conductive surface part of or passing through a polishing material on which the substrate is processed. A mechanical component of the polishing process is performed by providing relative motion between the substrate and the polishing material that enhances the removal of the conductive material from the substrate.
During ECMP processing, the conductive material is electrical biased by one or more contact elements. The contact elements are subject to corrosion and/or attack by processing chemistries, thereby resulting in diminished electrical conduction to substrates over a period of processing cycles. As the efficiency of the electrical contact is diminished, processing of a substrate is impaired. Moreover, sludge and/or other deposits may accumulate around the electrical contact, further obstructing the maintenance of good electrical biasing of the substrate through the contact element. Good electrical connections for biasing the substrate must be preserved in order to maintain robust process performance.
Thus, there is a need for an improved method and apparatus electrochemical processing.